In the prior art driller, the drilling head is installed at a clamper and then the clamper is installed to a grinding seat. A grinding wheel serves to grind the drilling head. The clamper is rotatable so that the front end of the drilling head is grounded to have a sharp surface.
However in the prior art the clamper cannot move along the grinding seat so that the length of the drilling head along the grinding seat must be calibrated by a calibration device. Thereby the calibration work is performed repeatedly. The operation is inconvenient and time consumed.